Socket contact with conductive elastomer contacting surface

ABSTRACT

This invention relates to a socket contact which provides a layer of conductive elastomer material along at least one wall of the socket hole. A contact in which a complete electrical circuit is established only when the pin and socket are fully mated may be provided by utilizing a conductive elastomer material which is conductive only when placed under compression.

United States Patent I 11 Dorrell et al.

SOCKET CONTACT WITH CONDUCTIVE ELASTOMER CONTACTING SURFACE Inventors:Robert Francis Dorrell, Des Plaines; Norman Richard Anderson, Cicero,both of I11.

Bunker Ramo Corporation, Oak Brook, 111.

Filed: June 5, 1974 Appl, No.: 476,612

Related U.S. Application Data Continuation of Ser. No. 323,867, Jan. 15,1973, abandoned.

Assignee:

U.S. Cl. 339/255 R, 339/DIG. 3 Int. Cl. H0lr 13/12 Field of Search339/147, 255, 256, 278,

References Cited UNITED STATES PATENTS 9/1960 Myers 338/100 1 Mar. 18,1975 Evanicsko, Jr 338/99 Cooney 339/256 R Harshman et a1 338/99DuRocher 338/114 Primary Examiner.loseph H. McGlynn Attorney, Agent, orFirm-Norton Lesser; Frederick M. Arbuckle ABSTRACT This inventionrelates to a socket contact which provides a layer of conductiveelastomer material along at least one wall of the socket hole. A contactin which a complete electrical circuit is established only when the pinand socket are fully mated may be provided by uti lizing a conductiveelastomer'material which is conductive only when placed undercompression.

2 Claims, 2 Drawing Figures a 2 J2 /19a 19 C5 SOCKET CONTACT WITHCONDUCTIVE ELASTOMER CONTACTING SURFACE This is a continuation ofapplication Ser. No. 323,867, filed Jan. 15, 1973, abandoned.

This invention relates to socket contacts for electrical connectors and,more particularly, to a socket contact having a conductive elastomercontacting surface.

BACKGROUND OF INVENTION Electrical connectors normally consist of a maleelement having one or more projecting pin contacts and a female elementhaving a like number of socket contacts. These socket contacts have apin-receiving hole in their forward face. Some sort of a metallic springmember is normally either mounted in the hole in engagement with thewalls thereof or is formed from the walls of the contact member itself.These springs serve to perform the dual function of physically retaininga pin in the socket and providing good electrical contact between thepin and socket,'the springs also serve to compensate for any slightmisalignment of a pin with its sockets.

While the springs presently utilized in socket contacts adequatelyperform the required functions, they do suffer from certainshortcomings. First, these springs normally engage the pin at a pointor, at best, over a relatively small area, thus providing a relativelyhigh contact resistance. The relatively small area of physical contactalso creates high bearing forces thereby generating excessive wear andgalling on thin electro-deposited precious metals normally applied oncontact surfaces. With repeated use, or as a result of pin misalignment,these springs may also become bent and distorted resulting in potentialspurious open circuit conditions. Finally, the forming and/or insertingof the springs is one of the more difficult and expensive operationsinvolved in making a socket contact. It would, therefore, be preferableifa simpler, less expensive, more reliable, technique could be developedfor providing physical and electrical contact with a pin inserted in thesocket contact. Such a technique should be adapted for providing contactover as large an area of the pin as possible while not creating acritical pin alignment condition.

Another problem with existing electrical connectors is that electricalconnection is normally effected as soon as the pin comes into contactwith the spring element in the socket even though the two connectorelements have not been fully mated. Where live lines are beingconnected, current may start flowing when only a point contact has beenestablished resulting in arcing and/or potential burn-out damage to thecontacts. In these situations, electrical contact should not beestablished until the connector elements are fully, orat leastsubstantially, mated. While connectors having this capability do exist,they are generally relatively complicated and expensive. A simple,inexpensive technique for preventing electrical circuit from beingestablished through a connector until its elements have been fully matedis thus required.

SUMMARY OF THE INVENTION In accordance with the above, this inventionprovides a socket contact for an electrical connector which contact hasa metallic contact body with a forward face having an elongated holeformed therein, the hole extending from the forward face. In place ofthe springs of the prior art, this invention provides a layer ofconductive elastomer material which is positioned in the hole alongatleast one wall thereof. Where the layer of elastomer material ispositioned only along the rear wall of the hole and the material is ofthe type which is conductive only when placed under compression, acircuit is completed through the socket contact only when the connectedelements are fully mated.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention as illustrated inthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cut-away side view of asocket contact of a preferred embodiment of the invention with a matingpin positioned therein.

FIG. 2 is a cut-away side view of an alternative embodiment of theinvention.

DETAILED DESCRIPTION Referring now to FIG. 1, it is seen that a socketcontact 10 having a metallic body 11 is provided which contact has awire crimp pocket 12 formed in its rear end and a pin-receiving hole 14in its forward face. A flange 16 is provided on the contact for use inretaining .the contact in a connector. It should be noted that pocket 12and flange 16 do not form part of the present invention. Thus, anysuitable means for permitting the connecting of a wire or other currentcarrying element to the contact may be utilized in place of pocket 12and flange 16 may be replaced by any other suitable contact retentionelement or may be eliminated completely.

The cross-sectional shape of hole 14 may be circular, square, or anyother desired shape with the peripheral surface I7 of the hole 14extending from one end 17a of said body 11. The shape of the hole 14depending on the cross-section of the metal pin or male contact 18 withwhich socket contact 10 is to be mated. Pin 18 has a peripheral surface19 and a radial or transverse forward end surface 190. The cross-sectionof hole 14 is slightly larger than that of the pin and the leading edgeof the hole is tapered so as to permit easy insertion of the pin, and topermit the socket to accept slightly misaligned pins. Along the reartransverse surface or wall 20 of hole 14 is a layer 22 of a conductiveelastomer material. Layer 22 may, for example, be an electricallyconductive silicone elastomer or other known conductive elastomer whichis normally conductive. However, for certain applications it ispreferable that layer 22 be of a material such as Pressex, manufacturedby Essex International, which material conducts electrical current onlywhen compressed. Where Pressex or a similar conductive elastomer isutilized for the layer 22, an electrical circuit is not establishedbetween socket 10 and pin 18 until the pin has been fully (or at leastsubstantially) inserted into the socket, compressing layer 22 to renderit conductive under the axial pressure of said pin against layer 22 andthe hole rear metal surface 19a defining the rear axial end of the hole.Thus, electrical contact over the entire contacting area is establishedbefore the electrical circuit is completed, preventing possiblearcing'or burn-out where live circuits are being connected.

Layer 22 may be rammed into hole 14 and held in by friction, may bemolded to the wall 20, or may be otherwise secured in the hole. However,regardless of how the elastomer is placed in the hole, the operation isrelatively simple and inexpensive. Further, the conductive elastomer isnot subject to deformation or other permanent distortion as the resultof use, pin misalignment, or other factors and, covering the entire rearwall of hole 14, the conductive elastomer makes contact with the pinover a-relatively large area. Thus, the socket of this invention isadapted for making reliable, relatively low resistance electricalcontact with an inserted pin even after repeated use, and possiblemisuse, of the socket.

FIG. 2 shows an alternative embodiment of the invention which differsfrom the embodiment shown in 7 FIG. 1 only in that hole 14 has aconductive elastomer layer 24 positioned therein which layer covers boththe rear wall and the side walls of the hole. The space 26 between theside-wall layers of conductive elastomer is substantially less than thecross-section of pin 18, so that the elastomer on the side walls is alsodeformed when a pin is inserted. This assures good electrical contactbetween the pin and the conductive elastomer over substantially theentire length of the pin which is in hole 14. If a Pressex-typeconductive elastomer is utilized with the embodiment of the inventionshown in FIG. 2, the opening 26 will have to be made quite small so asto assure adequate pressure on the conductive elastomer along the sidewalls to render the elastomer conductive. The portion of the conductiveelastomer layer near the front of the hole 14 is tapered slightly forease of pin insertion and to reduce the tolerances on pin alignment.

An improved socket contact has thus been provided. While the inventionhas been particularly shown and described above with reference topreferred embodiments thereof, it will be understood by those skilled inthe art that the foregoing and other changes in form and detail may bemade therein without departing from the spirit and scope of theinvention.

What is claimed is:

1. A socket contact for use in an electrical connector adapted toreceive a metal pin, said pin having a peripheral surface and atransverse forward end surface for establishing an electrical connectionbetween said pin and contact comprising:

a metallic contact body having an elongated hole formed therein with anelongated axis, said hole extending from one end of said body anddefined by an axially extending peripheral surface portion, a rear metalsurface on said body at a position spaced in one direction from said oneend of said body to define a rear axial end of said hole;

an axially extending layer of conductive elastomer material positionedin said hole with said layer of elastomer material having a peripheralsurface extending axially of said hole and engaging said peripheralsurface portion of said hole throughout the axial extent of theperipheral surface of said layer of elastomer material;

a rear surface on said layer of elastomer material engaged with the rearmetal surface defining the rear axial end of said hole; and

a forward surface on said layer of conductive elastomer material spacedfrom the one end of said body and transverse to the axis of said pin andhole with the forward surface of said layer of elastomer materialterminating the peripheral surface of said layer and having an areacorresponding to the area of said transverse forward end surface of saidpin and placing said layer of elastomer material under the axialpressure of said pin between the rear axial end of said hole and saidtransverse forward end surface to establish said electrical connectionas a low resistance electrical path through the transverse forward endsurface of said pin and the forward surface of said layer of elastomermaterial transverse to the axis of said pin without deformation ofeither said pin or socket contact in response to the insertion of saidpin in said hole to engage said layer of elastomer material under saidaxial pressure.

2. A contact as claimed in claim 1 wherein said layer of conductiveelastomer material has an annular portion integrally formed on saidlayer of elastomer mate rial engaging the peripheral surface portion ofsaid hole with said annular portion extending toward the one end of saidbody and defining an axially extending recess for receiving and engagingthe peripheral surface of said pin.

1. A socket contact for use in an electrical connector adapted toreceive a metal pin, said pin having a peripheral surface and atransverse forward end surface for establishing an electrical connectionbetween said pin and contact comprising: a metallic contact body havingan elongated hole formed therein with an elongated axis, said holeextending from one end of said body and defined by an axially extendingperipheral surface portion, a rear metal surface on said body at aposition spaced in one direction from said one end of said body todefine a rear axial end of said hole; an axially extending layer ofconductive elastomer material positioned in said hole with said layer ofelastomer material having a peripheral surface extending axially of saidhole and engaging said peripheral surface portion of said holethroughout the axial extent of the peripheral surface of said layer ofelastomer material; a rear surface on said layer of elastomer materialengaged with the rear metal surface defining the rear axial end of saidhole; and a forward surface on said layer of conductive elastomermaterial spaced from the one end of said body and transverse to the axisof said pin and hole with the forward surface of said layer of elastomermaterial terminating the peripheral surface of said layer and having anarea corresponding to the area of said transverse forward end surface ofsaid pin and placing said layer of elastomer material under the axialpressure of said pin between the rear axial end of said hole and saidtransverse forward end surface to establish said electrical connectionas a low resistance electrical path through the transverse forward endsurface of said pin and the forward surface of said layer of elastomermaterial transverse to the axis of said pin without deformation ofeither said pin or socket contact in response to the insertion of saidpin in said hole to engage said layer of elastomer material under saidaxial pressure.
 2. A contact as claimed in claim 1 wherein said layer ofconductive elastomer material has an annular portion integrally formedon said layer of elastomer material engaging the peripheral surfaceportion of said hole with said annulAr portion extending toward the oneend of said body and defining an axially extending recess for receivingand engaging the peripheral surface of said pin.